1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a trench element-isolating structure.
2. Description of the Background Art
Heretofore, in a semiconductor integrated circuit, elements are isolated for eliminating electrical interference between the elements during operation, and for independently controlling each element. In particular, a trench element-isolating structure is an essential structure for miniaturization of circuits.
It has been known that various problems arise if a silicon oxide film buried in a trench (hereafter referred to as xe2x80x9cburied oxide filmxe2x80x9d) is depressed from a surface of a substrate, and an indentation is formed, as disclosed in Japanese Patent Laid-Open No. H10-340950 (FIG. 13).
Even if the indentation is not formed, a large protrusion of the buried oxide film may result in dimensional variation in gate forming, or etching residues. Therefore, it is an important problem in determining the performance of an element to control the extent of protrusion of the buried oxide film from the surface of the substrate when a trench element-isolation structure is formed.
In order to make prevention of formation of indentation and the reduction of the extent of protrusion of the buried oxide film compatible, it is important to minimize variation of the extent of protrusion of the buried oxide film.
However, in conventional manufacturing methods, it was difficult to reduce the variation of the quantity of protrusion of the buried oxide film.
The present invention has been conceived to solve the previously-mentioned problems and a general object of the present invention is to provide a novel and useful method of manufacturing a semiconductor device.
A more specific object of the present invention is to reduce the variation of the quantity of protrusion of the buried oxide film.
The above object of the present invention is attained by a following method of manufacturing a semiconductor device.
According to a first aspect of the present invention, in the method, a laminated film including a thermal oxide film, a non-single-crystal silicon film and a silicon nitride film is formed on a substrate. The laminated film is patterned. An element-isolating trench is formed in the substrate, using the patterned laminated film as a mask. A buried oxide film is deposited in the element-isolating trench. After depositing the buried oxide film, the silicon nitride film is removed. Unnecessary portions of the buried oxide film are removed by chemical-mechanical polishing (CMP) using the non-single-crystal silicon film as a stopper film. The non-single-crystal silicon film and the thermal oxide film are removed.
According to a second aspect of the present invention, in the method, a laminated film including a thermal oxide film, a silicon nitride film, and an oxide film or a metal film is formed on a substrate. The laminated film is patterned. An element-isolating trench is formed in the substrate by using a patterned laminated film as a mask. After forming the element-isolating trench, the oxide film or the metal film is removed. A buried oxide film is buried in the element-isolating trench. Unnecessary portions of the buried oxide film are removed by CMP using the silicon nitride film as a stopper film. The silicon nitride film and the thermal oxide film are removed.
According to a third aspect of the present invention, in the method, a laminated film including a thermal oxide film, a non-single-crystal silicon film, and an oxide film or a metal film is formed on a substrate. The laminated film is patterned. An element-isolating trench is formed in the substrate using a patterned laminated film as a mask. After forming the element-isolating trench, the oxide film or the metal film is removed. After removing the oxide film or the metal film, a buried oxide film is buried in the element-isolating trench. Unnecessary portions of the buried oxide film are removed by CMP using the non-single-crystal silicon film as a stopper film. The non-single-crystal silicon film and the thermal oxide film are removed.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.